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Weak Bases Do Not Undergo Complete Dissociation Instead, Their Ionization Is A

The document discusses pH and how it is used to measure the acidity or basicity of water-based solutions. pH is measured on a scale from 0 to 14, with acidic solutions having a lower pH below 7 and basic solutions having a higher pH above 7. While strong acids and bases completely dissociate, weak acids and bases only partially dissociate, requiring consideration of their ionization constants and equilibrium concentrations to calculate pH. Most biologically relevant substances are weak acids or bases, making it important to understand how to calculate their pH using ionization constants, equilibrium concentrations, and ICE tables.

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Renie Boy Tabugon
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46 views2 pages

Weak Bases Do Not Undergo Complete Dissociation Instead, Their Ionization Is A

The document discusses pH and how it is used to measure the acidity or basicity of water-based solutions. pH is measured on a scale from 0 to 14, with acidic solutions having a lower pH below 7 and basic solutions having a higher pH above 7. While strong acids and bases completely dissociate, weak acids and bases only partially dissociate, requiring consideration of their ionization constants and equilibrium concentrations to calculate pH. Most biologically relevant substances are weak acids or bases, making it important to understand how to calculate their pH using ionization constants, equilibrium concentrations, and ICE tables.

Uploaded by

Renie Boy Tabugon
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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In chemistry, pH is a scale used to specify how acidic or basic a water-based

solution is. Acidic solutions have a lower pH, while basic solutions have a higher
pH. At room temperature (25 °C), pure water is neither acidic nor basic and has a
pH of 7.

Unlike strong acids/bases, weak acids and weak bases do not completely dissociate
(separate into ions) at equilibrium in water, so calculating the pH of these solutions
requires consideration of a unique ionization constant and equilibrium
concentrations. Although this is more difficult than calculating the pH of a strong
acid or base solution, most biochemically important acids and bases are considered
weak, and so it is very useful to understand how to calculate the pH of these
substances. The same basic method can be used to determine the pH of aqueous
solutions of many different weak acids and bases.

An aqueous solution of a weak acid or base contains both the protonated and
unprotonated forms of the compound, so an ICE table can be made and used to
plug in concentrations into an equilibrium constant expression. The ionization
constant for the acid (Ka) or base (Kb) is a measure of how readily the acid donates
protons or how readily a base accepts protons. Because you are calculating pH, you
must solve for the unknown concentration of hydronium ions in solution at
equilibrium.

The pH of a weak base falls somewhere between 7 and 10. Like weak acids,
weak bases do not undergo complete dissociation; instead, their ionization is a
two-way reaction with a definite equilibrium point

Denomination pH range
Ultra acidic < 3.5
Extremely acidic 3.5–4.4
Very strongly acidic 4.5–5.0
Strongly acidic 5.1–5.5
Moderately acidic 5.6–6.0
Slightly acidic 6.1–6.5
Neutral 6.6–7.3
Slightly alkaline 7.4–7.8
Moderately alkaline 7.9–8.4
Strongly alkaline 8.5–9.0
Very strongly alkaline > 9.0

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